According to me: never enough
According to my wife: way more than necessary
No counting broken bit or stuff I got as props for a photo project:
Cambo SC 4x5
3 Mamiya M645's (I only really use one; the other two are "insurance".
Detrola 127 format (does 127 count as medium format?)
Pentax ME Super (x2)
Konica Autoreflex (inherited from father in law)
Voigtlander Vito B (inherited from my father; first "good" camera I used, immense sentimental value)
Olympus Pen FT (needs repair)
Maybe my wife is right . . .